The present invention relates to a movable enclosure for the replacement of contaminated equipment, as well as for the transportation of the same to a discharge unit, where they can undergo appropriate treatments or repairs. The invention also relates to a complementary confinement casing or sheath for such an enclosure.
It is known that installations for the analysis and treatment of radioactive materials must be located in completely tight confinement cells. Therefore, these installations must be remotely controlled from the outside of the cell and any handling operation involves the performance of a precise intervention process leading to no break in the seal of the cell.
In particular, when the maintenance of such an installation requires the replacement of a mechanical part, it is necessary to remove the latter from the cell. The intervention process must then enable this operation to take place, whilst protecting the personnel present at all times. This presupposes that the cell seal is at no time broken and that the contaminated part is never in direct contact with the ambient air when it is removed from the cell.
At present, this type of operation is carried out by means of flexible plastic material sacks or bags (generally polyvinyl chloride) in which the part is enveloped during its removal from the cell and which simultaneously maintain the seal of the latter. The thus enveloped part is introduced into a transportation casket or container and the tight seal of the plastic material bag is brought about by means of a double system of slide valves respectively connected to the cell and to the casket and effecting the weld of the plastic bag. Such a system is described in the reports of the 13th Conference of the American Nuclear Society of 15-18 Nov. 1965 at Washington, pp. 118/9, article by J. A. Evans entitled "Transfer device for irradiated materials".
The description of the operation given in this document makes it clear that such a process takes a long time and makes it necessary to equip the confinement cells with special equipment. Moreover, the opening of the tightly sealed bag at the discharge unit is necessarily accompanied by a break in the confinement, which is obviously not satisfactory from the standpoint of the safety or personnel.
In addition, the use of the conventional intervention procedure requires numerous manipulation and transportation operations. Thus, it is firstly necessary to bring the empty casket from the discharge unit to the cell in which the part to be replaced is located and then the latter has to be transferred from the cell to the casket using a process comparable to that described in the aforementioned publication. The casket containing the part then has to be transported to the discharge unit, where the part is removed from the casket. A casket containing a new part is then transported up to the cell and the new part is transferred into the latter. Finally, the casket containing the defective, contaminated equipment is brought to the discharge unit. It can be seen that this takes a relatively long time, which is not really compatible with the operating conditions imposed on such installations.
It is also clear that the number of transportation operations relative to the contaminated equipment leads to an increase in the risks of accidents. From this standpoint, it should also be noted that the method consisting of packaging contaminated parts in flexible plastic bags offers the supplementary risks of these bags tearing during transportation as a result of a shock or impact, which would lead to a complete loss of their effectiveness.